Probably a one-stop shop for sourcebook-y material, the Star Wars: The Visual Dictionary series is full of high-quality photos of characters, props, costumes, vehicles and the like, short biographies and the like. Nothing in-depth, but enough to run a shortish game that covers as much story as a movie at least. From checking The Force Awakens book I know enough about the Republic from a two-page spread to use it in-game.
The Art Of books are full of used and unused concept art, model shots, storyboards and the like. The prequels involved so much brainstorming that major elements of the Clone Wars like Asajj Ventress came from unused designs.
The novels have less immediate “take this and run with it” use than the visual books, providing plots and descriptive imagery. The Aftermath series by Chuck Wendig is the big hitter here, big hardback novels charting the time between trilogies, while Before The Awakening by Greg Rucka covers events closer to the new film and gives a look at how the Resistance and First Order work within the Republic Senate.